Tachymetric sight



July 3, 1951 s. G. lssERsTEDT TACHYMETRIC SIGHT 2 Sheets-Sheet 1 Filed'0ct. 11, 1946 om o 0MM aNvaN-roa 5.6. aSSERSTE-r WSF July 3, 1951 s. G.lssl-:RsTEDT TACHYMETRIC SIGHT 2 Sheets-Sheet 2 Filed Oct. l1, 1946 ,w/PNw E E@ L mw mn Sh@ /f m M C m MQ H l il. fifi? mm Mr Il 1 um .wv\ /JfNVNTO 5.6. BSSERSTET Patented July 3, 19751 Si F FICE;

TCHYMETRIC SIGHT Siegfried. Gordon.. Issersteac; 'comme omnia Canada,lassignerA to Corex Limited, Toronto,

Qntarin. Canada, a;` company of. Ontario.

Application G'ctoher. 111946-5 SerialNoi 702,66'65 2Claims. (Cl.339-49):

rela-teelten tachymetric in; which thee-sighting: spot .of the sight:isi corrected?.`

fon range, relative. ot thev target:v andg. eaectsof winnt. and.temperaturaonthe` flight; of the: pizoiectile1 tos gicethe: gun'. thezproper lead..

More particularly.. lioweven'. the present; inven-r timaL electricalegyro` tach-ymetriexsights: imwhi'eni the; deflectionsftoi the.vsighting.v spettereobtainedi through. shifting; the magnetic contreienthe gyrafbyichanging the: currentim the: apro control by' novelattenuator means..

` In. this aai'pli'cation` theinventioir relates a.y

spe'eic: cla-esci sighttfbr which@ a. mirror is'V- mounted; oma.gyrosc'opie dev-ice: and will'.

t-be lcv-eli atY timesf1` A light, source directs ai. beamtowardfthe-mirror and: the is re iiecteds.thierefroin` to fall. onta a:sighting plate-v haring. cross-hairs andi illuminate this plate:-

suilicientlytmprovidnasightingzspot. The si'ghtf, ingplateis. ixed in.movement; relative to the` movementot the gunbarrel. asis thegyroscopica.

and The: g-y-roscopic device; how-"-Ik ererg, means. whereby the;position; of the; mifrormay be eifectedi hy'variolrs; magnetic eld'sgenerate'da in.: vaaicnslcoil'e' in. conjunction: wit-lr.v a.

magnenpet.. im knownmanner as; regards the principlesrimiolued.

The attenuator used to varpithezcurrenttin ther gua-' coilsi iniAconventional computers; consieteJ on. a; seriestofz. rotaryv switches.and. Ixedre# adiustment steps;v The. conventional. attenuatorV thushas.- certairr inherent. disadvantages asi,- maintenance on slip;rings.` and. contactV brushes;-

enlarge'v number of attenuators-..each. being; made. dpr-ot; separaterresistors placedi in. series; to! give:-

currents* and'. thus; limiting.:v the.` accuracyA to asfraction on thevalues ofeacl'r; resistor to the` attenuator as; a. whole; lastlythe-great-num,-V`

beni cfa manual: adiustments.. which. the; gunnerA must-maketocompensater for. wind direction;

- With: a views to :overcoming: such: disadvantages.,

iti primaryl obieet of, the present. inventiampr prende-a.. combinan@ oncomputer.- amr teeny rr-ietnicrL sight` wliereinallzv sightingadjustments'.

are made automatically so thatxit isinerely. nec.= essere;A for the:gunnentoakeep'. the: spotting sight on the target.

Another. object of thepresent.Y invention is to provide; a: computercapable. of more. accurate. adljustment than prientypesl and; whichv is.less'exepensive: to: rnanuf-acture.:

A'. furthen obj eenk invention is. tot: provide. a. computer innwhicli;allzresistorsf are stationary; thus eliminatingrslipi rings;andrcontact. brushes..

Astillifurther objectotz the; present. inventionv isitoeprovidei a.computer-1 intwhich one. standard;

variable' resistenV replaces; fou-r separate. attenuatars i'nafcrmerlmechanisms.

A still; furtl'nen objectv the present. inventicmiszto providea-icbmputen otithe proposedtype.

imwhichf. the electrical output.- may be. changed;

without changing;- the. electrical circuit.

Withithese; and'A ottienzobiects. in view the; presont: inventiomgenerally comprises: mechanical.

means. operatively! related with the. movement; of.

a cooperating gun lbarrel",whereby.the.v values. ofv variable'resistancesare varied, in anv electrical..

circuit' tmchange .the-:currents owinglin the elec.'

ioincuita; thereby tol provide a controllable. disposition and.strength.. of; magneticJ elds,.,an.

armature freely' suspended in said elds. andcarrying9 af. mirror".tofpostiorr aa sighting; spot, .said

l mirror: and. armaturev being rotatedifor gyroeiii`ect,..and`regula-tieni of. said gyro, eiect by: said4 fields.:whereby;said.f.-sighting.spot is positioned relative to said gun incompensating! manner to allow; for wind.- direction. and velocity,relative movement of; the target; andlthe path of. the. projectilerelative to theelevation of the gun.

The invention willbeclearly understoodv by ref.-

erence to the following; detailed specification taken in conjunctionwith the accompanying drawings.

Eig l ist ai schematiview of; the' proposed. com-Av puter; and.

liigcv 2--is,1a.sectiona1.view otthefsight and more particularly.I the:gyra unit which is` regulated byv electrical circuit relation: with:the.- device of. Figi..

1,;.anda further, showing; a. motor which. rotates the sightsforgyroieiect.

Rieterringtofthe: drawings it will.v be notedV that. the; device is,rcomprised: of" a. number of units.

some being independentzandothers; being coop:` erative in nature.Generally... however, these units; may' be indicated with reference. totheir. prime: function( `aa.. an. elevatior-i` compensatingL unitari, a.horizontal. compensating unit.. Bg. a,A gyra unit C, manual adjustingmeans D, remote transmission means or Selsyn system E, wind velocityadjustment F, range resistor G, and temperature compensating resistor H.

The unit A provides a means of gaining suicient lead of the gun barrelover the sighting spot to compensate for the path of the projectile.However, it also governs the correction for Wind to be applied by otherunits with respect to the elevation of the gun.

The unit B compensates for wind in all quadrants in the horizontal planeand provides the required lead of the gun barrel to the sighting spot orin some cases may provide an appropriateV lag. The unit C, irrespectiveof the other units, be-

-ing attached to the gun, provides the proper lag in the sighting spotto compensate for movement of the target due to gyro effect. Units A andB qualify this condition and further enter their respective effectssupplementary to the primary gyro effect in unit C.

Unit D provides adjustment of unit B by manual means for direction ofwind.

Unit E is a remote Selsyn Vsystem which can govern unit D and therebycompensate for direction of the wind automatically.

The wind velocity resistor F governs the current in and hence theresultant effects of the units A and B and their. contribution to thegyro unit C. The overall current attainable in the electrical circuitcorrecting for Wind direction is thus qualified by manual adjustment ofunit F and is thus governed thereby in this one respect.

The range resistor G controls the overall current owing to theelectrical circuit of the whole mechanism and qualifies the lag of thegyro unit by manual adjustment to compensate for range. The electricalcircuit is governed by the resistor G in such a manner that at minimumrange a maximum current flows in the electrical circuit and hence aminimum of lag, whereas at maxi. mum range, very little current flowsand a max-.- imum of lag is provided. In order that this fundamental beabsolutely clear, it is necessary to mention that the electrical circuitso mentioned here only refers to the range coil so that when the currentin range coil is a minimum, then by virtue of range resistor G thecurrent available to units A and B must be a maximum. By the very natureof the corrections applied by units A and B, it must be so as will beevident in a moment of reflection.

Lastly, the unit H is a thermostat means of controlling a variableresistor which compensates for temperature changes in the mechanisms sodescribed, by controlling the overall current supplied to all electricalcircuits. 1 v

Mechanical characteristics The unit A is comprised of a shaft l0'operatively related with the vertical movement or elevation of the gun.Appended to shaft II'Iv is a cam Il being designed in itsperipheralcontour to regulate the sweep of cantilever arms I2 andA I3 over taperedresistors I4 and I5 respectively, in a desired relation to the elevationof the gun, in order to compensate for-relative movement of' gun andtarget in the vertical plane and for the path of the projectile in thevertical plane. Arms I2 and I3 have sliders I2a and I3a. which engagetapered resistors I4 and I5 to pick offA resistances therefrom. On theupper extremity of-v shaft I0 and xed thereto is an indicator IIl and adial I1 fixed in relation to a bubble horizon. l

4 Rollers I8 and I9 provide smooth control of arms I2 and I3 by cam IIand are mounted on said arms.

The unit B is comprised of shaft which is mechanically related bysuitable means (not shown) to the movement of the gun barrel so that thearc of horizontal sweep of the gun will beduplicated' by* .correspondingrotation of the shaft 20. A dial 22 is mounted in fixed relation withrespect to the zero bearing of the gun which, in the case of aninstallation of a gun on a seagoing vessel, would be the course of thevessel. The indicator 2| mounted on the upper extremity of shaft 20 atvany time will indicate the bearing of the gun in its horizontal sweeprelative to the course of the vessel. A gear 23 is appended to a bushing24 which is mounted freely on shaft 2D. The bushing 24 carries a cam 25rotatably mounted thereon and having a contour engaging switch arms 26and 21, the contour being designed 'to provide movement of said arms inpredetermined relation with respect to the rotation of the bushing 24bydifferential gear means 24a. Bushing 24 carries a gear 28 appendedthereto which engages idler gears 29 and 30 of said idlers being mountedin a differential gear housing 3I connected to mounting cam and cam 32.Gear 33:.is fixed to shaft 20 and engages idler gears 29 and 30 topro-vide a differential Y assembly whereby, if-thebushing 24 is heldstationary and shaft 20 isrotated, the cams will be caused to rotateone-half the radial amount but-.in the, same direction as the rotationof the shaft..20. Bushing 24 is held fixed by Way .of gear 23,.to ='vunit D and governed thereby according to the die. rection of the wind.The cam 32 is designed on its peripheralcontour to:.position arms 34, 35by bearing: on rollers 36, 3.1 in a predetermined vrelation which is afunctionA ofthe relative movement of gun and target andiwind effects.Gear384 merely carries anindicator 39 which points to the` direction ofthe wind relative -Jto the zero bearing of the gun on scale ofjdial 2-2and for this funci tion gear 38 must be freely mounted on shaft:

20. vThe arms 34, 35 have sliders 34a and 35a,

which engage the .tapered resistors 40 and 4I and.; pick off resistancevalues therefrom Which.are= determined by the position ofthe arm infunc-z tion above mentioned.

- Unit C is shown in Fig. 2 and is the gyro unitn of the sight of thegun.- The gyro unit is comin prised of an exterior casing V (Fig. 2)havinga; iield coil 5I mounted thereon; said casing beingl termed themagnet pot. This magnet'apot has a cover 52 formed substantially'asshown to ac-.. commodate a bearing 53 uponwhich a bushingA 54.ismounted. The'bushing 54.' forms a univer#- sal carriage with the'gring55forfan armature rod 56 connected to a mirror 51. and having an alu-.1minum dish armatue` 58 appended ,to its lowerextremity. It is to benoted that a motor 59 ro-`l tates thebushing 54 by means ofa belt 60cause" ing-.rotation of the armature assembly and gyro` action thereby.Posts 6I, 52, 63, 64 (Figs. 'l and 2.) Aextend .upwardly from the baseof. .the mag-I netfpot 50 Atoprovide air gap 65 4between-their. upperends a and the downwardlydepending: portion 52a of the cover 52 and inwhich the dish` armature 58 floats. -Therefore, since themag-l inet pot,cover, and postsv are "made of 'similar'.

flux conducting material, the intensity of.- the magnetic flux passingthe gaps may be controlled:Y by suitable energizaton of coils 66, 68 on`post 6I; v61, 69 on post 62; and coils10 and 1I (Fig. lle:

7f5onp'osts 63and 64 respectively. These coils are! attacca? f shown'-schematically in'A C'is operatively related in the conventionalmannen:directly toV the movementl of the barrel off thegun and hence the mirror51 due to its gyroscopic rotation will lag the travei of the barrel tocompensate for relative movementofthe target.

The unit D is an adjusting means comprised off a shaft 80 with a handknob 8| mounted on its upper extremity. Gears 82` andi 83v are fixedtir-shaftA 80. Clockwise rotation of shaft 80,

Fig. 1-. The whole unit` therefore, causes counterclockwise rotation offbustlingl 2470i unit B by intermeshng-A of gears 82`-andf 231; at thesametime causing proportional clockwise rotation: ofgear 38' byintermeshing of' gear 83land gear 38 with andidler gear 84? mountedtherebetween. At: thelower extremity of shaft 80 is: a receiver 85V-which. controls rotation of shaft'v 80? by'remote control from unit E.

The unit E is a remote precisioning system suchv as a Selsyn. Atransmitter 90 is operatively -relatedl with a shaft 9|, said shafthaving a wind vane- 92S mounted thereon which is designed to point intothe wind. 'I-hus rotation of shaft 9| cau'sedl by the indicating or winddirection vane 92.* will be automatically transmitted to shaft 80 of.unit B by remote control by Selsyn system indicated` by parts 85 and90.

E-lectrz'cclY circuit Considering the electricalA circuit, it will beAnoticed. that its function is; to govern the magnetic ilux existing inthe gaps. 65 to eiect the positioning of the armature thereby. This is'.ac-

complished by changing resistance components:

ture. Current then flo-ws from the temperaturecompensating resistorI-0Il` to the wiper 'I-02`5 of a variable range resistor |03, one endoff said resistor being connected to the-non-grounded end oithe'el'd.coil 5I- of the magnet-pot. The other' end of said range resistor isconnected! tothe-nongrounded end?` off resistor I4; of uni-t A.Alternatively, the circuit so` shown may be incorpo-v` rated in a radarcircuit by means' off a. suitable switching mechanism |041. The currentflows from the point ofconnection to resistor I4 also through a Xedvoltage dropping resistor |05 through a wind` force resistor assemblywhichis' comprised of resistors |05 and |07 and a common wiper |08connectedV to resistors I5 and 4I (being in parallel with respect toground) and which distributes the-current fromV these resistors betweenground and theY resistor |05 since resistor |01 is grounded at one end;

Energizatzon of coils Asi has been previouslyv pointed out, the fieldcoil 5| of the magnet potV may be energized byv voltage drop through a.temperature correction resistor and a ranger-resistor-or by radar tap asindicated.

The tangentelevation coils-68.'` andl 69 arecon nected in series betweenground andi the slider I'Zzr on the resistor I4.

termined: by the operation of un-it`V A.

I Thel current through'the horizontal wind coils;

Thus theeV current` de rivedi forthe operation of these coils` willi be"de 6. 6'6l andY 61: isfvaried by' the: unit- A, the unit; B, arretchanged in directionbyithe position of` the swltclr arm'L 26T of." theunitv B.. In this respect, the; rte-- sistor I5 offuniti A and theresistor 40 of' unit B- andfthe contour of cam 25 are involved.

The cross wind coils I0 and'. 1I are. energized. by current which ischangedy in direction andi. modified' in magnitude by the unit" BAthrough thevmedium of cam 25 andj tapered resistor M.. Thefvalue'ofcurrent from. resistor 4I further de pendslon adjustment wind forceresistorassem-r bly1 If08 Itmay alsol be'v noted that' the current.'deriveclf by virtue of wind force resistor asseme bly. |08' isdependent' upon. unit A. in tapered re sistorv I'Il` which is connected.to the supply voltage as previously described. It is` apparenttherefore,that the current: in the cross wind coils mand 'II is both a function ofunit A and unit Bi..

In'. respect to viiux conditions, it is to be as.:- sumed that the coilsare assembled in. the'magL netpot as formerly described, but aremounted. sothatthe flux from. coil 68 acts. additivelywit'l'r coi-1:'5`I` and' either additively` or otherwise with coil 661depending on. thedirection ofcurrent 'ow;

. in` coil 66` and according to; the. action of there versing4 switch26:. of unit B.. Further, that.: the direction ofnux from coils 69V and(il.` is opposite to'. that existing in coils` liand` 66. at all timesa.

Again that thev coils I0 and 'II mounted on posts'. Iil and 64respectively, are mounted. in suoliv manneras tobe. opposed magneticallyatk all times;`

with respect to one another but that'. the direc-- tion. ofi magneticflux achieved therefrom is de;- pendent'. upon thev direction ofcurrentV ow dea-- termined: by; the reversing. switch 2T of the-,unitiB. Still again, that the coil. 5I of the magnet pot 50. has currentiiovvingA therethrough asi formerly described which causes fluxthereby'tofbe owing always in thesame direction.

The-magnetic flux accruing from coil 5I is vari'.- able in magnitudeaccording tothe range by the range resistor |02. Coil 5I being the rangecoilf makes compensation for range by dampingv or" adding to theresultant ux of. all the other coilsi depending: upon the magnitude anddirectionofi current flowin the latter. "Thus, Where the mag;-neti'clnux. from coils and 69V is: dominant. thel coil 5I acts in adamping sense whereas if. the? magnetic flux in the coils 66 and 6T isdominant: coil 5I' will actin an additive sense.. Itwill there-Y forebeapparent that in someinstances, the range coi15'I` may generate suicientilux to neutralize the eiect ofthe other coils at one of the posts: oreven reverse' the polarity of the post as estab--` lished bythedirection of current in the coil'. mounted thereon. At the Sametime,some of the other posts may have theres-ultant ux addedtof by the coil5I. neutralize the effect of the other coils and' in this way causes alagging in their effect by making resul-tant elds so weak as not toinstantly position the dish 58 relative to the dispositionl of ux at theposts. Hence, the lagof the gyro unit is' varied by the current in coil5 I. When the range'A is short' the current is large andl thev lag ofthe gyro is small and thus the gun will only point aH small amount aheadof the target'. If, however,A the range is long; the current in coil 5|will bei small' and thus the gyro unit and the sighting," spot willlagmore and give the gun a greater leach Operation The range coil 5Ithus tends tolthe projectile by adjustment of the range resistor |03 toensure that the proper amount of current is. flowing in the range coll5I, or that radar is supplying current thereto by way of switch |04, andfurther that the direction of flow of magnetic flux in the gaps 65 isfrom vthe cover 52 to the posts 6I, 62, 63 and 64. Therefore, let it beassumed that each post is South at the working end or merely S Similarlythe cover 52 must be North or N. Considering the coils mounted aspreviously described, the following cases will first reveal the resultderived from each component of the mechanism and then trace it back byway of magnetic, electrical, and mechanical operation to the adjustmentof each unit by automatic means or otherwise according to its nature.

Case 1.-Gun bearing zero, elevation zero, wind bearing .aero (blowingfrom the gun to the target) .-Here the horizontal wind coils 66, 61contribute nothing since no current is flowing through them. This isevident by noting that the source from which resistor 40 of unit Breceives current is from resistor I5 of unit A and since slider |30Jwill be contacting to ground as shown, no current can pass throughcontact 34a to the horizontal Wind coils. The cross wind coils 10, 1|contribute no flux to posts 63, 64 since they are supplied with currentthrough a switch 21 by slider 35a which picks off voltage from resistor4| and the slider 35a will Ibe connecting to ground. Thus, in this caseonly the range coil 5I and tangent elevation coils 68 and 69 arerelevant and unit A Will be at zero, unit B will be adjusted to zer'o onthe scale including indicator 39 and further unit E will be pointing inthe direction of the Wind on zero bearing.

Case 2.-Gun bearing 90 degrees, elevation aero,

wind bearing aero, with reference to ee'ro bearing of gun as before-Thetangent elevation coils 68, 69 on posts 6I, 62 will not receive currentdue to the adjustment of unit A as before. The cross Wind coils and 1Ion posts 63 and 64 will receive current of such direction that post 63will have flux deducted therefrom and post 64 will have iiux added. Thedirection of current iiow is determined by the switch 21 and the cam 25in operative relation by unit B with the bearing of the gun. The currentis derived then from slider 35a which, however, in this instance ridesat the upper end of the'resistor 4I due to the gear relation betweencams 25 and 32. The horizontal wind coils 66 and 61 will receive nocurrent as before since the slider I3a will connect to the grounded endof resistor I5. Thus, in this condition where the cross wind is from theright, the

mirror 51 will be dipped to the left to throw the sighting spot in thatdirection and provide the appropriate lead for the gun.

Case 3.-Gnn bearing 180, lother conditions remaining the same-Thetangent elevation coils will be unaffected as before. The horizontalWind coils 66, 61 on posts 6I 62 will receive no current as previously.The cross wind coils 10 and 1I will receive no current by way of switch21 since slider 35a will rest at the grounded end of resistor 4I due toposition of cam 32. It is to be noted that due to positioning of arms 34and 35 on cam 32, the ycurrent picked off by one of their cooperatingsliders is a maximum where the current picked off the other is zero.This case is similar to Case 1.

Case 4.-G'nn bearing 270, other conditions remaining the sama-This issimilar to Case 2 except that the direction of current in the cross windcoils is reversed since the wind is from the left here,'and by virtue ofcam 25 switch 26 will reverse the flow of current. The source of currentin this respect is by Way of slider 34a as per Case 2. Here the mirrorwill tip to the right causing the barrel to lead the sighting spot andcompensate for cross Wind thereby.

In all of the above cases where the elevation of the gun is zero it willbe noted that the slider I2a rides at the upper end of the resistor I4and re-v ceives current accordingI to range as determined.

by the range resistor |03 which distributes the positive voltage betweenthe coil 5| and the resistor I4 in accordance with the range adjust.-ment. Ther-e is thus some effect in the tangent elevation coils whichtheoretically would be zero at zero range but in the practical sensethis need not be provided for and for this reason the resistor I0 willat any adjustment of the range resistor receive some current which wouldbe of negligible effect at short range.

Case 5.-Gu.n bearing zero, elevation 90, wind bearing cera-This differsfrom Case l in thatY the horizontal wind coils will receive currentsince slider I3a will no longer ride at the grounded end of resistor I5but will be positioned thereon at a maximum point determined by the camI of the.

crease the S in post 62 in addition to the S polarity already on theends of the posts by virtue of range coil 5 I. The tangent elevationcoils 68 and 69 will contribute a maximum of N to post 6I and a maximumof S to post 62 respectively. The mir-f ror 51 will then be tippedforward causing a lowering of the sighting spot and a leading of thebarrel of the gun upward.

Case 6.-Gun bearing 180?, other conditionssame as Case 5.-All conditionswill be the same as Case 5 except the horizontal wind coils which.' willreverse polarity due to a change of direction of current by the changedposition of switch 26 determined by contour of cam 24, thus tending todecrease the lead of the gun upwards of the sighting spot.

From a consideration of the foregoing examples and noting the effectsmentioned, the results of the operation of the sight for any position ofthe gun can be clearly visualized.

Case 7.-Gun bearing 45, elevation 45, wind direction .aerei-In this casethe tangent elevation coils 68 and 69 will be effected according to theposition of slider I2a which will be sub-I stantially midway alongresistor I4, the latter being constructed according to a cosinefunction. The cross-Wind coils 10 and 1I will be effected by the windforce resistors |06 and |01 governing voltage on resistor 4I whichdistributes its resistance according to a sine function and the slider awill pick off voltage for these coils. The horizontal Wind coils 66 and61 are dependent upon the voltage pick off resistor I5 by slider I5awhich in turn feeds the resistor where the slider 34a determines thecurrent to be appliedv The resistor I5 is formed accordto the coils. ingto a sine function, whereas the resistor 4l is formed according to acosine function. The slider I3 acts to compensate for elevation windforce or variation with one force according to elevation whereas theslider 34a determines theamount of correction for the horizontaleffect.l

The tangent elevation.

La.' 9 of the wrindas regardsthe horizontal bearing of the gun relativeto its zero bearing.

I Operation summary The tachymetric sight .measures the relative :rateof Achange of position between the target 'zand the gun barrel position,vand corrects the .sighting spot to. give the gun barrel a lead `.whichis in proportion to the .rate of vchange in posiition. The computermakes 'corrections for the `range and adjusts the sighting spot tocomipensatefor .the effects of temperature 4and wind oni the projectile.

`When the gunner rotates the vgun to -keep the `target on the sightingspot, lor moves 'it Iup land down, this will .affect the 'gyro unit,mounted on the gun, in a mannerzto 4move the `sighting spot up or down,`or-right .or .left, in order to compensate for the range, the relativemovement of the target, and the .'.eiects of wind and temperature on theflight of fthe projectile.

The-lag of the gyro unit lbe'l'iind the -position of the gun barrel iscontrolled by the strength of the range coil, which surrounds the magnetpot of the sight. When the range is short, the current through this coilwill be large and the lag of the gyro unit will therefore be small. Ifthe range is long, and therefore the shell is in the air for a longertime, the current through the range coil will be weak. Therefore, thegyro unit and sighting spot will lag behind the position of the gunbarrel and, therefore, if the sighting spot is kept on the movingtarget, the gun barrel will be directed ahead of the target when therange is long. The sighting spot is deflected to compensate for windconditions and tangent elevations in the following manner. The

magnet pot of the gyro unit contains the coils described mounted atright angles around the centre thereof and by energization of thesecoils, the magnetic centre of the gyro unit may be changed and willthereby7 affect the position of the sighting spot.

By means of these coils, therefore, the sighting spot may be deflectedeither up or down, which affects the elevation of the gun barrel, or tothe right or left which affects the bearing of the gun barrel, e. g. ifthe gun fires at right angles to the wind, a correction in the bearingof the gun barrel is required; whereas, if the gun barrel fires directlyinto the wind or with the wind, the direction of the bullet will not beaffected by the wind and, therefore, no correction of the gyro unit isrequired. The computer makes these corrections automatically byenergizing the coils in the magnet pot which tends to move the sightingspot to the right or left.

The large coil in the magnet pot which affects the lag of the gyro unit,and thereby the sighting spot, and which is affected by the range of thetarget only, has been referred to as the range coil. The coils in themagnet pot of the sight, the energizing of which causes the sightingspot to move to the right or left, are referred to as the cross windcoils. The coils which move the sighting spot up and down are referredto as the tangent elevation coils, and the horizontal wind coils.

It will thus be evident that the present computer comprises acomparatively simple device in contrast with former types and that itwill not only be less bulky but due to its nature, will cut down theduties of the gun crew considerably by substituting automatic for manyof the former manual adjustments. Further, the ac- 10 rcuracy of `thepresent computer is not limited to .increments ofthe attenuators 'butonly by the accuracy of the camy contours and lost Ymotion inmechanicaltransmission, all of which is a Vminimum and probably of lessconsequence than `the variables in the gun itself.

What I claim as ymy invention is:

. 1. .In 4a .sighting devicefor guns, having `an illuminated movablesighting spot governed by the position of a mirror, .including means forkgyroscopically 4mounting the mirror .in a ymagnet .pot which is:energized by a main electrica-l :coil .in a @primary electrical.circuit `and :including .a plurality of coils in a secondaryYelectricalfcircuit magneticallyfcoupled with yand .designed tomodifythe magnetic eld .effectsof thermain .coil on the gyrcscopica-l.'mounting :to .correct 'the sighting spot, :and .wherein the pluralityof coils are arranged in groups as cross-Wind coils, horizontal windcoils, and tangentfelevationcoils; the com- ,bination comprising, :meansconnecting .said y.cir-

cuits in lparallel between positiveVV voltage and ground and includingvariable range resistor means for distributing positive voltage betweenthe circuits according to range, a variable elevation wind forceresistor having one end thereof connected to ground, means for applyinga positive voltage to the other end of said resistor according to windforce, a slider on said elevation wind force resistor, cam means foractuating said slider in accordance with elevation to select a maximumvoltage from said elevation wind force resistor when the elevation ofthe gun barrel is 90 and minimum voltage therefrom when the elevation ofthe gun barrel is zero, means operatively related to the gun barrel andproviding movement of said slider over said elevation wind forceresistor in accordance with the movement of said barrel, a variablehorizontal wind resistor having one end connected to said slider and theother end connected to ground, a horizontal wind slider designed to pickoff a maximum voltage from said horizontal Wind resistor when thehorizontal gun bearing is 0 or 180 and zero voltage therefrom when thehorizontal bearing of the gun is or 270, double-pole double-throw switchmeans having a common pole connecting to said horizontal wind slider,and connecting the horizontal wind coils in series to ground, and meansoperatively related to the gun barrel for actuating the horizontal windslider and said switch means in accordance with the horizontal bearingof the gun with regard to wind direction.

2. In a sighting device for guns, having an illuminated movable sightingspot governed by the position of a mirror, including means forgyroscopically mounting the mirror in a magnet pot which is energized bya main electrical coil in a primary electrical circuit and including aplurality of coils in a secondary `electrical circuit magneticallycoupled with and designed to modify the magnetic field effects of themain coil on the gyroscopical mounting to correct the sighting spot, andwherein the plurality of coils are arranged in groups as cross-windcoils, horizontal wind coils, and tangent elevation coils; thecombination comprising, means in said secondary circuit for distributingelectrical current to said plurality of coils in accordance with Windeffects and comprising a shaft operatively related in its rotation withthe horizontal sweep of the gun barrel, a bushing freely mounted on oneend of said shaft, means for rotating said bushing in accordance withthe direction of wind, a differential gear housing freely mounted onsaid bushl 1 ing and said shaft and carrying a switching cam and aslider cam, differential idler gears mounted in said housing andextending inwardly thereof to engage a gear xed to said bushing and agear fixed t0 said shaft, double-pole double-throw switch means actuableby said switch cam and electrically connected to the cross-wind coilsand the horizontal wind coils to determine the direction of current owin the latter, a voltage source, horizontal wind resistor means andcross-wind resistor means connected electrically in parallel between thepositive voltage of said source and ground, and slider arms connectingto said switch means and slidable over said resistors disposed to beactuated by said slider cam to vary the electrical current in said coilsaccording to the bearing of the gun relative to the direction of wind.

SIEGFRIED GORDON ISSERSTEDT.

REFERENCES CITED The following references are of record in the iile ofthis patent:

Number Number 20 574,704 578,958

l UNITED STATES PATENTS Name Date Thomson Sept. 11,1888 Methlin May 11,1926 Paulus et al. Dec. 12, 1933 Roberton Dec. 19, 1933 Gillmor et alDec. 18, 1934 Gourdon July 26, 1938 Smulski Dec. 2, 1941 Esval Aug. 18,1942 Kaufman Jan. 9, 1945 Doyle et al May 7, 1946 Lovell et al Mar. 18,1947 Darlington Apr. 13, 1949 Johnson Apr. 19, 1949 Lakatos et al Jan.16, 1951 FOREIGN PATENTS Country Date Great Britain Jan. 17, 1946 GreatBritain July 18, 1946

